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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 747 · 40 questions
TalentJR

How to do it in your head (Guess, divide, average): Division: round the divisor to the nearest ten and find the closest multiple of it. Square root: guess the nearest whole root, then divide the number by your guess. Average the guess and the answer of the division, and round to 1 decimal place.

NameDateTime takenScore ___ / 40
  1. 1.√90 to 1 decimal place? (a) 9.5 (b) 9.6 (c) 9.4 (d) 9.3
  2. 2.Best estimate of 778 ÷ 29? (a) 2600 (b) 26 (c) 260
  3. 3.Best estimate of 728 ÷ 26? (a) 24 (b) 240 (c) 2400
  4. 4.Best estimate of 3888 ÷ 43? (a) 970 (b) 9700 (c) 97
  5. 5.Best estimate of 6112 ÷ 86? (a) 680 (b) 6800 (c) 68
  6. 6.√65 to 1 decimal place? (a) 8.0 (b) 7.9 (c) 8.1 (d) 7.8
  7. 7.√23 to 1 decimal place? (a) 4.9 (b) 4.8 (c) 5.0 (d) 4.7
  8. 8.√22 to 1 decimal place? (a) 4.9 (b) 4.7 (c) 4.6 (d) 4.8
  9. 9.Best estimate of 1456 ÷ 88? (a) 160 (b) 1600 (c) 16
  10. 10.Best estimate of 537 ÷ 44? (a) 130 (b) 13 (c) 1300
  11. 11.Best estimate of 389 ÷ 26? (a) 1300 (b) 130 (c) 13
  12. 12.√61 to 1 decimal place? (a) 7.9 (b) 8.0 (c) 7.7 (d) 7.8
  13. 13.Best estimate of 1921 ÷ 46? (a) 3800 (b) 38 (c) 380
  14. 14.√28 to 1 decimal place? (a) 5.5 (b) 5.4 (c) 5.3 (d) 5.2
  15. 15.√50 to 1 decimal place? (a) 7.2 (b) 7.1 (c) 7.0 (d) 6.9
  16. 16.Best estimate of 3713 ÷ 78? (a) 460 (b) 4600 (c) 46
  17. 17.√79 to 1 decimal place? (a) 8.8 (b) 8.6 (c) 8.9 (d) 8.7
  18. 18.Best estimate of 836 ÷ 24? (a) 4200 (b) 420 (c) 42
  19. 19.Best estimate of 529 ÷ 32? (a) 180 (b) 1800 (c) 18
  20. 20.√67 to 1 decimal place? (a) 8.2 (b) 8.4 (c) 8.3 (d) 8.1
  21. 21.Best estimate of 4112 ÷ 62? (a) 6900 (b) 690 (c) 69
  22. 22.Best estimate of 732 ÷ 56? (a) 12 (b) 1200 (c) 120
  23. 23.√94 to 1 decimal place? (a) 9.8 (b) 9.9 (c) 9.7 (d) 9.6
  24. 24.Best estimate of 3222 ÷ 68? (a) 4600 (b) 460 (c) 46
  25. 25.Best estimate of 1510 ÷ 26? (a) 500 (b) 5000 (c) 50
  26. 26.Best estimate of 5987 ÷ 83? (a) 75 (b) 7500 (c) 750
  27. 27.Best estimate of 1646 ÷ 82? (a) 210 (b) 21 (c) 2100
  28. 28.Best estimate of 642 ÷ 24? (a) 320 (b) 3200 (c) 32
  29. 29.√56 to 1 decimal place? (a) 7.7 (b) 7.6 (c) 7.5 (d) 7.8
  30. 30.√34 to 1 decimal place? (a) 5.8 (b) 5.9 (c) 5.6 (d) 5.7
  31. 31.√26 to 1 decimal place? (a) 5.1 (b) 5.4 (c) 5.2 (d) 5.3
  32. 32.Best estimate of 5001 ÷ 66? (a) 7100 (b) 710 (c) 71
  33. 33.Best estimate of 1653 ÷ 38? (a) 41 (b) 4100 (c) 410
  34. 34.√58 to 1 decimal place? (a) 7.6 (b) 7.7 (c) 7.5 (d) 7.8
  35. 35.√59 to 1 decimal place? (a) 7.9 (b) 7.8 (c) 7.6 (d) 7.7
  36. 36.Best estimate of 3343 ÷ 83? (a) 4200 (b) 42 (c) 420
  37. 37.Best estimate of 5026 ÷ 59? (a) 84 (b) 840 (c) 8400
  38. 38.√77 to 1 decimal place? (a) 8.7 (b) 8.9 (c) 8.8 (d) 8.6
  39. 39.Best estimate of 2094 ÷ 23? (a) 1050 (b) 10500 (c) 105
  40. 40.Best estimate of 1144 ÷ 23? (a) 570 (b) 5700 (c) 57

Answer key

  1. 9.5
  2. 26
  3. 24
  4. 97
  5. 68
  6. 8.1
  7. 4.8
  8. 4.7
  9. 16
  10. 13
  11. 13
  12. 7.8
  13. 38
  14. 5.3
  15. 7.1
  16. 46
  17. 8.9
  18. 42
  19. 18
  20. 8.2
  21. 69
  22. 12
  23. 9.7
  24. 46
  25. 50
  26. 75
  27. 21
  28. 32
  29. 7.5
  30. 5.8
  31. 5.1
  32. 71
  33. 41
  34. 7.6
  35. 7.7
  36. 42
  37. 84
  38. 8.8
  39. 105
  40. 57

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